Preform inspection device comprising an image acquisition device

Abstract

Preform inspection device comprising an image acquisition device. The inspection device comprises a preform (1) transport device (14) arranged to move the preform (1) at least rotationally about its axis (A) at a predetermined rotational speed, and an image acquisition device (16) arranged to acquire images in a fixed field of view (18). The image acquisition device (16) is arranged to acquire at least two images of the preform (1) on the transport device (14) when said preform (1) is in the field of view (18) of said image acquisition device (16), the interval between the acquisition of the two images being determined at least as a function of the rotational speed so that the preform (1) has two different angular orientations in said acquired images. Figure for the abstract: 2

Description

Title of the invention: Device for inspecting a preform comprising an image acquisition device

[0001] The present invention relates to a device for inspecting at least one preform made of thermoplastic material comprising a body extending along an axis, the inspection device comprising a device for transporting the preform arranged to move the preform at least in rotation around its axis at a predetermined rotation speed and an image acquisition device arranged to acquire images in a fixed field of view.

[0002] A preform is a container blank that allows a container to be produced by blowing the preheated preform. Such a preform comprises a body that is deformed during blowing and a neck that is already molded to its final shape and which remains unchanged during blowing.

[0003] To produce quality containers, it is important to ensure that the preforms used have satisfactory parameters before they are deformed. Thus, it is known to inspect the preforms before they are introduced into the molds of a blowing wheel in which the preforms are formed into containers by blowing.

[0004] The inspection is carried out for example from images of each preform acquired and analyzed by an image processing device. To the extent that the acquisition of a single image of the preform is not sufficient to obtain a complete and usable representation of the preform, several image acquisition devices are provided, arranged to acquire different images of the same preform from different angles. To do this, several image acquisition devices can be distributed around a fixed preform or several image acquisition devices can be arranged along a circulation path of a preform rotating on itself to obtain images of the preform in different orientations.

[0005] However, the use of several image acquisition devices complicates the structure of the inspection device as well as the image processing device which must manage images coming from different sources for each preform. Thus, the inspection device is bulky, complex and expensive.

[0006] One of the aims of the invention is to overcome these drawbacks by proposing an inspection device with a simplified structure while still allowing the entire preform to be inspected.

[0007] To this end, the invention relates to an inspection device of the aforementioned type, in which the image acquisition device is arranged to acquire at least two images of the preform on the transport device when said preform is in the field of view of said image acquisition device, the interval between the acquisition of the two images being determined at least as a function of the rotation speed so that the preform has two different angular orientations in said acquired images.

[0008] By taking advantage of the fact that the preform rotates on itself and by appropriately choosing the interval between two shots, the inspection device makes it possible to obtain a complete image of the preform by means of a single image acquisition device. Thus, the structure of the inspection device is simplified and its size is reduced. In addition, the exploitation of the acquired images is also simplified, these images coming from only a single source.

[0009] The inspection device according to the invention may comprise one or more of the following characteristics, considered alone or in any technically conceivable combination: - the transport device is further arranged to move the preform in translation along a scrolling path substantially perpendicular to the axis of the preform, said scrolling path passing within the field of view of the image acquisition device, the preform extending in two different zones of the field of view and according to two different angular orientations when the two images are acquired, - the field of view of the image acquisition device is substantially parallel to the axis of the preform, the two acquired images showing two different areas of the body of the preform, - the inspection device further comprises a device for illuminating the body of the preform, said image acquisition device and said preform illuminating device extending on either side of the preform, - the inspection device further comprises a device for illuminating the body of the preform, said image acquisition device and said preform illuminating device extending on the same side of the preform, - the field of view of the image acquisition device is substantially perpendicular to the axis of the preform, the two acquired images showing two different zones of a collar of the preform, said collar extending in a plane substantially perpendicular to the axis of the preform. - the inspection device further comprises a device for illuminating the collar of the preform, said image acquisition device and said lighting device extending on the same side of the collar of the preform, - the image acquisition device is offset from the axis of the preform, the images acquired by said image acquisition device showing a section of the collar of the preform, - the rotation angle of the preform between the two images acquired by the image acquisition device is between 60° and 120°, - the inspection device further comprises a device for processing the images acquired by the image acquisition device, said processing device being arranged to determine at least one parameter of the preform from the acquired images and to compare said determined parameter with a desired value of said parameter, - the parameter of the preform determined by the processing device is chosen from the following parameters: shape of the body of the preform, distribution of material in the preform, presence of a defect in the material of the preform, presence of a mark on the preform.

[0010] According to another aspect, the invention also relates to a method for inspecting a preform using the inspection device described above, the method comprising the following steps: - placing a preform on the transport device and moving the preform in rotation around its axis at a predetermined rotation speed, - acquiring at least two images of the preform, the interval between the acquisition of the two images being determined as a function of the rotation speed so that the preform presents two different angular orientations in said acquired images.

[0011] According to a characteristic of the method, it comprises an additional step of processing, implemented by a processing device, the images acquired by the image acquisition device, the processing being arranged to determine at least one parameter of the preform from the acquired images and to compare said determined parameter with a desired value of said parameter.

[0012] According to one embodiment, the image processing device is produced in the form of software, or a software brick, executable by a processor of the inspection device further comprising a memory associated with the processor.

[0013] The memory of the inspection device is then capable of storing image processing software. The processor is then capable of executing the image processing software.

[0014] In a variant not shown, the image processing device is produced in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array) or an integrated circuit, such as an ASIC (Application Specific Integrated Circuit).

[0015] When the image processing device is produced in the form of one or more software, that is to say in the form of a computer program, also called a computer program product, it is furthermore capable of being recorded on a medium, not shown, readable by a computer. The computer-readable medium is, for example, a medium capable of storing electronic instructions and of being coupled to a bus of a computer system. For example, the readable medium is an optical disk, a magneto-optical disk, a ROM memory, a RAM memory, any type of non-volatile memory (for example FLASH or NVRAM) or a magnetic card. A computer program comprising software instructions is then stored on the readable medium.

[0016] The invention also relates to a computer program comprising software instructions which, when executed by a computer, implement a method of inspecting a preform as defined above.

[0017] Other aspects and advantages of the invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0018] [Fig.l] - [Fig.l] is a schematic perspective representation of a preform to be inspected,

[0019] [Fig.2] - [Fig.2] is a schematic representation seen from above of a device for inspecting a preform according to an embodiment of the invention,

[0020] [Fig.3] - [Fig.3] is a schematic representation of the two images acquired of a preform to be inspected by means of the inspection device of [Fig.2],

[0021] [Fig.4] - [Fig.4] is a schematic perspective representation of the neck of a preform to be inspected, and

[0022] [Fig.5] - [Fig.5] is a schematic representation seen from below of a device for inspecting a preform according to another embodiment of the invention.

[0023] With reference to [Fig. 1], a preform 1 is described which can be inspected by an inspection device according to the invention. Such a preform 1 is intended to form a container after steps of heating the preform 1 and blowing, or stretch-blow molding, the preform 1.

[0024] Such a preform 1 essentially comprises a body 2 and a neck 4, the neck 4 being more particularly shown in [Fig. 4]. The body 2 extends along an axis A and has, for example, the shape of a test tube extending between a bottom 6 and a neck 4, which forms an open end 8 of the test tube.

[0025] The neck 4 comprises for example a flange 10 extending from a radial plane substantially perpendicular to the axis A projecting towards the outside of the body 2. Such a flange 10 forms for example a gripping surface for the preform 1 and the container produced from the preform 1.

[0026] The part of the preform 1 extending from the collar 10 to the end open 8 comprises for example a thread 12 allowing a cap to be fixed on the container made from the preform 1.

[0027] The preform 1 is made of a thermoplastic material, for example polyethylene terephthalate (PET). The thermoplastic material is for example translucent, that is to say that the preform 1 allows light to pass through, in particular through the body 2. Alternatively, the thermoplastic material is opaque and does not allow light to pass through. The body 2 of the preform 1 becomes malleable when the body 2 of the preform is heated above the glass transition temperature of the thermoplastic material during a step of heating the preform 1 so that the body 2 can then be deformed to form the body of a container when compressed air is injected into the preform 1 through the open end 8 during a step of blowing or stretch-blowing the preform 1.In a known manner, the neck 4 of the preform 1 is not heated during the heating step and remains undeformed during the blowing or stretch-blow molding step so that the neck 4 of the preform 1 has the shape of the neck of the container made from the preform 1.

[0028] In order to produce a good quality container, it is necessary to ensure that the preform 1 is itself of good quality and complies with certain parameters. Thus, the preform 1 must have the desired shape, which implies in particular that the body 2 actually extends along its axis A and does not deviate from it (a phenomenon known as the "banana shape"). The thermoplastic material must also be correctly distributed in the preform 1 and not include impurities or air bubbles trapped in the material. The presence of scratches and / or a defect in the joint plane must also be avoided. Finally, the preform 1 must have given dimensions with a certain tolerance margin. It is understood that this list of parameters is given only as an example and that other parameters may be taken into account to ensure that the container produced from the preform will be of good quality.

[0029] To verify that the preform complies with these parameters, it is planned to inspect the preform 1, for example before and / or after heating the preform 1, by means of an inspection device, which will now be described.

[0030] According to a first embodiment shown in Figs 2 and 3, the inspection device is more particularly arranged to inspect the body 2, the neck 4 and the thread 12 of the preform 1.

[0031] The inspection device according to the first embodiment comprises a transport device 14 for the preform 1. The transport device 14 is arranged to move the preform 1 at least in rotation around its axis A. In other words, the transport device 14 is arranged so that the preform 1 rotates on itself. For this purpose, the transport device 14 comprises for example a support (not shown) on which the preform 1 is placed, the preform 1 being for example fitted onto the support by its open end 8, the support being movable in rotation around the axis A of the preform 1 when the latter is received on the support. Such a support is notably known under the name of “turntable”. The transport device 14 is arranged to rotate the preforms at a predetermined and for example adjustable rotation speed. The rotation speed depends notably on the diameter of the preform.

[0032] According to one embodiment, the transport device 14 is further arranged to move the preform in translation along a travel path D substantially perpendicular to the axis of the preform 1. The travel path D may have any appropriate shape depending on the travel path of the preform 1 in a container production facility. Indeed, the inspection device for the preform 1 is for example integrated into the container production facility and the transport device 14 of the inspection device is then for example a device for transporting a succession of preforms 1 in a processing unit of the container production facility. Thus, by way of example, the transport device 14 is the device for transporting a succession of preforms in an oven of a container production facility, the oven being arranged to heat the preforms during a heating step as described above.In this case, the inspection device is for example arranged at the entrance of the furnace to inspect unheated preforms or at the exit of the furnace to inspect heated preforms. It is understood that the container production installation may comprise several inspection devices, for example one arranged at the entrance of the furnace, one in the middle of the furnace and one at the exit of the furnace. Alternatively or additionally, the transport device 14 may be the device for transporting a succession of preforms from one preform processing station to another processing station. According to the example shown in [Fig. 2], the travel path D is curved, the inspection device being arranged at a bend in the preforms in a furnace.

[0033] When the transport device transports a succession of preforms, the distance between two successive preforms is called the “pitch” of the transport device. The rotation speed of the preforms 1 may depend on the pitch of the transport device. Indeed, the larger the neck diameter of the preform, the larger the pitch of the transport device. For example, the larger the pitch, the more the rotation speed of the preforms increases at the same machine speed.

[0034] The inspection device further comprises an image acquisition device 16 arranged to acquire images of the preform 1 to be inspected when the latter is moved by the transport device 14. More particularly, the image acquisition device 16 is arranged to acquire images in a field of view 18 and the preform to be inspected moves in the field of view 18 when the image acquisition device 16 acquires images of the preform 1.

[0035] According to the first embodiment shown in Figs. 2 and 3, the field of view 18 of the image acquisition device 16 is substantially parallel to the axis A of the preform 1. In other words, the image acquisition device 16 acquires images of the body 2 of the preform 1, from the bottom 6 to the open end 8 thereof. Such images may also be called front images of the preform 1, as shown in [Fig. 3].

[0036] The image acquisition device 16 is arranged to acquire at least two images of the preform 1 when the latter moves, at least in rotation, in the field of view 18 of the image acquisition device 16. The time interval between the two image acquisitions is determined at least as a function of the rotation speed of the preform 1 so that the preform 1 has two different angular orientations in said acquired images. In other words, the time interval between the two image acquisitions is such that the two acquired images show two different zones of the body 2 of the preform 1. The angular orientations of the preform 1 in the two acquired images are more particularly chosen so that they make it possible to obtain a complete representation of the body 2 of the preform 1 from the two acquired images, that is to say that the two acquired images make it possible to show the entire periphery of the body 2 of the preform 1.In the two angular orientations chosen, account is taken in particular of the shadow zones masking a part of the body 2 of the preform 1 on one of the images, taking into account the lighting of the preform 1 during the acquisition of the images as will be described later. In other words, one of the acquired images shows in particular the part or parts of the body 2 of the preform 1 which extends into the shadow zone or zones of the other image and vice versa.

[0037] When the preform 1 is furthermore transported in translation by the transport device 14, the time interval between the two image acquisitions is furthermore determined by the speed of translational movement of the preform 1, in particular so that the preform 1 remains in the field of view 18 of the image acquisition device 16 when the second image is acquired. Indeed, the preform 1 moves opposite the image acquisition device 16, which is fixed as is the field of view 18, when it is transported in translation by the transport device 14, as shown schematically in [Fig. 2] which shows a preform 1 in solid lines during the first shot and the same preform in dotted lines during the second shot.This also implies that the preform 1 extends in two different areas of the field of view 18 and in two different angular orientations when the two images are acquired so that the preform 1 extends at one location. different from the image in the two acquired images. This can be seen in [Fig. 3], in which a preform 1a extends to the right of the first acquired image (left image in [Fig. 3]) and to the left of the second acquired image (right image in [Fig. 3]). It can also be seen that, in the second acquired image, a second preform 1b has entered the field of view 18 of the image acquisition device 16, so that the second acquired image can be used with a third acquired image to carry out the inspection of the second preform 1b.

[0038] The rotation angle of the preform 1 between the two acquired images is for example between 60° and 120°, more particularly between 70° and 110°. The minimum value of 70° between the two acquired images makes it possible in particular to ensure that the parts of the preform masked by one or more shadow zones in one acquired image are visible in the other acquired image. By way of example, the rotation angle of a preform 1 between the two acquired images is approximately 90° for a pitch of 40 mm and approximately 75° for a pitch of 50 mm between two successive preforms.

[0039] As indicated previously, the preform 1 is illuminated during the acquisition of the images by the image acquisition device 16, which makes it possible to improve the quality of the acquired images and the inspection of the preform which results from the exploitation of these images. For this purpose, the inspection device comprises a lighting device 20 of the preform 1 arranged to illuminate the preform 1 during the acquisition of the two images by the image acquisition device 16.

[0040] According to the first embodiment, the lighting device 20 is more particularly arranged to illuminate the body 2 of the preform 1, in particular to backlight the body of the preform 1. In other words, according to the first embodiment, the image acquisition device 16 and the lighting device 20 of the preform 1 extend on either side of the preform 1, as shown in [Fig. 2], so that the light emitted by the lighting device 20 passes through the preform 1 before reaching the image acquisition device 16. The lighting device 20 is for example arranged to emit light in the visible or near infrared range. Thus, the lighting device emits, for example, light having a wavelength between 380 nm and 2500 nm, more particularly between 380 nm and 780 nm for the visible range and between 800 nm and 2500 nm for the near infrared range.In this case, the image acquisition device 16 is for example a camera working in the visible or near infrared range.

[0041] Such backlighting is permitted when the preform 1 is translucent. In this case, two images may be sufficient to carry out the inspection of the entire body 2 of the preform 1. When the preform 1 is made of an opaque material, the lighting device 20 is for example arranged on the same side of the preform 1 as the image acquisition device 16 and more than two images may be required to perform the inspection of the entire body 2. In this case, the rotation angle of the preform 1 between the different images may be greater.

[0042] A diffuse filter and / or a bandpass filter may be added in front of the lighting device 20 in order to improve the illumination of the preform 1 by improving the diffusion of the light emitted by the lighting device 20 and / or by limiting the wavelength range of the light emitted by the lighting device 20.

[0043] The inspection device further comprises a device 22 for processing the images acquired by the image acquisition device 16 arranged to determine at least one parameter of the preform 1 from the acquired images and to compare said determined parameter with a desired value of said parameter. The processing device 22 is more particularly arranged to detect and / or measure one or more particular parameters of the preform 1 on the acquired images. Such a processing device 22 is for example produced in the form of software, or a software brick, executable by a processor of the inspection device further comprising a memory associated with the processor, as described previously.The processing device 22 is for example arranged to detect and / or measure at least one of the following parameters: shape of the body of the preform, distribution of material in the preform, presence of a defect in the material of the preform, presence of a mark on the preform.

[0044] According to a second embodiment, the inspection device is more particularly arranged to allow the inspection of the collar 10 of the preform 1, as shown in [Fig. 5]. Such an inspection device comprises the same elements as the inspection device of the first embodiment, namely a transport device 14 of the preform 1, an image acquisition device 16, a lighting device 20 and a device 22 for processing the images acquired by the image acquisition device 16. These elements have for example the same characteristics as those described with reference to the first embodiment and only the arrangement of these elements relative to the preform 1 is modified.Thus, the transport device 14 of the preform 1 is arranged to move the preform 1 at least in rotation around its axis A, and according to one embodiment also in translation along a movement path D and the image acquisition device 16 is for example a camera working in the visible or near infrared range. According to additional characteristics, the lighting device 20 is for example arranged to emit light in the visible or near infrared range and the processing device 22 is for example produced in the form of software or a software brick.

[0045] Only the specificities of the inspection device according to the second method of rea- lization will now be described with reference to [Fig.5]. The other characteristics of the inspection device according to the second embodiment are identical to those of the first embodiment.

[0046] According to the second embodiment, the field of view 18 of the image acquisition device 16 is substantially perpendicular to the axis A of the preform 1. In other words, the image acquisition device 16 acquires images of the collar 10 of the preform 1, the latter extending in a plane perpendicular to the axis A of the preform 1 as described previously. Thus, the image acquisition device 16 is for example arranged above the preform 1 and faces the collar 10 of the preform 1, unlike the first embodiment in which the image acquisition device 16 faces the body 2 of the preform 1.

[0047] According to one embodiment, the image acquisition device 16 is offset relative to the axis A of the preform 1. That is to say that the field of view 18 of the image acquisition device 16 is not centered on the axis A of the preform 1, but on a part of the periphery of the preform 1 in a radial plane perpendicular to the axis A of the preform 1, as shown in [Fig.5]. Thus, the image acquisition device 16 is arranged to acquire images of sections 10a, 10b, 10c of the collar 10. These sections pass in front of the image acquisition device 16 while the preform 1 rotates on itself and is possibly moved in translation along the scrolling path D, as shown in [Fig. 5] where the different sections 10a, 10b, 10c of the collar 10 of the same preform 1 have been shown facing the image acquisition device 16.The different sections 10a, 10b, 10c are arranged to enable a representation of the entire collar 10 to be obtained from the acquired images. The fact of not centering the field of view 18 on the axis A of the preform 1 makes it possible to improve the quality of the representation of the collar 10 obtained from the acquired images. Indeed, when the field of view 18 is centered on the axis A of the preform 1, the neck 4 and the thread 12 or the body 2 project shadows onto the collar 10 and mask certain areas thereof, which prevents a complete representation of the collar 10 from being obtained.

[0048] According to a preferred embodiment, in the case of the inspection of the collar 10, the image acquisition device 16 is arranged to acquire at least three images of the collar 10, that is to say three images showing more particularly three sections 10a, 10b, 10c of the collar 10. By “show more particularly”, it is meant that the image can contain more than the representation of the section of which it is desired to acquire the image but that this section is more particularly visible and clear on the image without the presence of a shadow that could mask part of it. Thus, in the case of the inspection of the collar 10, the angle of rotation between each image acquisition is 120° maximum in order to obtain a representation of the entire collar 10.

[0049] According to the second embodiment, the lighting device 20 extends on the same side of the collar 10 as the image acquisition device 16. Thus, when the image acquisition device 16 extends above the preform 1, the lighting device 20 also extends above the preform 1.

[0050] The image processing device 22 operates in the same way as for the first embodiment and makes it possible to determine and / or measure at least one parameter of the collar 10 of the preform 1. It will be noted more particularly that the image processing device 22 can be used to locate the position of a mark on the collar 10 making it possible to detect the angular orientation of the preform 1. Such an angular orientation can in fact be important for the subsequent processing of the preform 1 and / or of the container obtained from the preform 1, as known per se.

[0051] It is understood that a container production facility may comprise at least one inspection device according to the first embodiment and at least one inspection device according to the second embodiment in order to allow inspection of all aspects of each preform.

[0052] The inspection device described above makes it possible to inspect preforms in a simple, precise and inexpensive manner, in particular because it only uses a single image acquisition device 16.

Claims

Claims

1. Device for inspecting at least one preform (1) made of thermoplastic material comprising a body (2) extending along an axis (A), the inspection device comprising a transport device (14) for the preform (1) arranged to move the preform (1) at least in rotation about its axis (A) at a predetermined rotation speed and an image acquisition device (16) arranged to acquire images in a fixed field of view (18), characterized in that the image acquisition device (16) is arranged to acquire at least two images of the preform (1) on the transport device (14) when said preform (1) is in the field of view (18) of said image acquisition device (16), the interval between the acquisition of the two images being determined at least as a function of the rotation speed so that the preform (1) has two different angular orientations in said acquired images.

2. Inspection device according to claim 1, wherein the transport device (14) is further arranged to move the preform (1) in translation along a scrolling path (D) substantially perpendicular to the axis (A) of the preform (1), said scrolling path (D) passing in the field of view (18) of the image acquisition device (16), the preform (1) extending in two different zones of the field of view (18) and according to two different angular orientations when the two images are acquired.

3. Inspection device according to claim 1 or 2, in which the field of view (18) of the image acquisition device (16) is substantially parallel to the axis (A) of the preform (1), the two acquired images showing two different zones of the body (2) of the preform (D-

4. Inspection device according to claim 3, further comprising a device (20) for illuminating the body (2) of the preform (1), said image acquisition device (16) and said device (20) for illuminating the preform (1) extending on either side of the preform (1).

5. Inspection device according to claim 3, further comprising a device (20) for illuminating the body (2) of the preform (1), said image acquisition device (16) and said device (20) for illuminating the preform (1) extending on the same side of the preform (1)

6. An inspection device according to claim 1 or 2, wherein the field of view (18) of the image acquisition device (16) is substantially perpendicular to the axis (A) of the preform (1), the two acquired images showing two different zones of a collar (10) of the preform (1), said collar (10) extending in a plane substantially perpendicular to the axis (A) of the preform (1).

7. Inspection device according to claim 6, further comprising a lighting device (20) for the collar (10) of the preform (1), said image acquisition device (16) and said lighting device (20) extending on the same side of the collar (10) of the preform (1).

8. Inspection device according to claim 6 or 7, wherein the image acquisition device (16) is offset relative to the axis (A) of the preform (1), the images acquired by said image acquisition device (16) showing a section (10a, 10b, 10c) of the collar (10) of the preform (1).

9. Inspection device according to any one of claims 1 to 8, wherein the angle of rotation of the preform (1) between the two images acquired by the image acquisition device (16) is between 60° and 120°.

10. Inspection device according to any one of claims 1 to 9, further comprising a device (22) for processing the images acquired by the image acquisition device (16), said processing device (22) being arranged to determine at least one parameter of the preform (1) from the acquired images and to compare said determined parameter with a desired value of said parameter.

11. Inspection device according to claim 10, in which the parameter of the preform (1) determined by the processing device (22) is chosen from the following parameters: shape of the body of the preform, distribution of material in the preform, presence of a defect in the material of the preform, presence of a mark on the preform.

Images